add pi. fix upstream issue #6 using pr #35

use the fix xqjibz recommended. upstream (mourner) never merged xqjibz's pull request because it would've broken dependent apps. it was suggested to merge the pr with a major version increment in order to avoid dependent apps automatically updating, but that suggestion was never heeded. my repo doesn't have dependent apps right now so i can go ahead and just solve this issue.

suncalc.js

@@ -38,7 +38,7 @@ var e = rad * 23.4397; // obliquity of the Earth
 function rightAscension(l, b) { return atan(sin(l) * cos(e) - tan(b) * sin(e), cos(l)); }
 function declination(l, b)    { return asin(sin(b) * cos(e) + cos(b) * sin(e) * sin(l)); }
 
-function azimuth(H, phi, dec)  { return atan(sin(H), cos(H) * sin(phi) - tan(dec) * cos(phi)); }
+function azimuth(H, phi, dec)  { return PI + atan(sin(H), cos(H) * sin(phi) - tan(dec) * cos(phi)); }
 function altitude(H, phi, dec) { return asin(sin(phi) * sin(dec) + cos(phi) * cos(dec) * cos(H)); }
 
 function siderealTime(d, lw) { return rad * (280.16 + 360.9856235 * d) - lw; }

test.js

@@ -38,7 +38,7 @@ var heightTestTimes = {
 t.test('getPosition returns azimuth and altitude for the given time and location', function (t) {
     var sunPos = SunCalc.getPosition(date, lat, lng);
 
-    t.ok(near(sunPos.azimuth, -2.5003175907168385), 'azimuth');
+    t.ok(near(sunPos.azimuth, 0.6412750628729547), 'azimuth');
     t.ok(near(sunPos.altitude, -0.7000406838781611), 'altitude');
     t.end();
 });
@@ -64,7 +64,7 @@ t.test('getTimes adjusts sun phases when additionally given the observer height'
 t.test('getMoonPosition returns moon position data given time and location', function (t) {
     var moonPos = SunCalc.getMoonPosition(date, lat, lng);
 
-    t.ok(near(moonPos.azimuth, -0.9783999522438226), 'azimuth');
+    t.ok(near(moonPos.azimuth, 2.1631927013459706), 'azimuth');
     t.ok(near(moonPos.altitude, 0.014551482243892251), 'altitude');
     t.ok(near(moonPos.distance, 364121.37256256194), 'distance');
     t.end();